悬浮物浓度对水下光照和初级生产力的影响

采用太湖湖泊生态系统研究站生态实验室的模拟生态槽进行水动力模拟实验研究(1999年5月8日～6月24日),探讨了水动力的扰动引起悬浮物的增加、改变水下光强的分布,并由此造成了初级生产力的变化.结果表明,无论是静止还是小水流、大水流状态,水下光强随深度都是按指数规律衰减;在静止状态下,槽水清澈见底,光衰减系数为1m-1左右,到小水流和大水流时,由于动力的扰动、悬浮物浓度的增加,光学衰减系数增加到2m-1和4m-1左右,真光层深度也由最初的4m降到2m、1m;对光学衰减系数、真光层深度与悬浮物浓度进行线性和幂函数回归,发现他们之间的相关性很好,反映了风浪扰动引起水中悬浮物增加是改变水下光照分布的主要原因;在静止状态下,由于槽水清澈,强光作用下表面存在光抑制现象,最大初级生产力出现在04～06m,其他情形光抑制很弱或基本上不存在,最大初级生产力出现在0～02m.

Experimental study on underwater light intensity and primary productivity caused by variation of total suspended matter

The simulation experiment was carried out in Taihu Laboratory for the lake ecosystem research from May 8 to June 24 in 1999.In order to find the distribution of light intensity and variation of primary productivity due to the increase of total suspended matter caused by water flow,the attenuation law of underwater light intensity,the relationship between the diffuse attenuation coefficient,the light euphotic depth and the total suspended matter,and the effects of light on primary productivity were studied.The results show that the light intensity attenuated as the depth increased,showing the good negative index correlation under not only the immobile condition but also weak and strong water flow.From immobile condition to weak and strong water flow,the diffuse attenuation coefficient increases from 1 m^-1 to 2 m^-1 and 4 m^-1,and euphotic depth decreases from 4 m to 2 m and 1 m.There are a good linear correlation between diffuse attenuation coefficient and total suspended matter as well as euphotic depth.Under immobile condition,the maximum primary productivity was recorded between 0.4 m and 0.6 m due to light inhibition at surface water shined by strong light.Under other circumstance,the maximum primary productivity was recorded between 0 m to 0.2 m due to the increase of the total suspended matter caused by water flow.